Honeywell has developed a new air conditioning system for urban air mobility (UAM) and electric aircraft. The first to be equipped with the new oil-free Micro Vapor Cycle System (MicroVCS) will be Eviation’s in-development Alice conventional takeoff and landing electric commuter airplane.
MicroVCS saves on weight by eliminating oil used for lubrication, which Honeywell said will also reduce maintenance costs. The vapor-cycle system’s refrigerant is Honeywell’s Solstice R1233zd, a low-pressure, non-flammable, “environmentally-conscious” hydrofluoroolefin. Cooling capacity is about 1,130 BTU/min (20 kW) at typical hot-day ground conditions, according to Honeywell. System weight, including a structural frame, is about 140 pounds for an aircraft of Alice’s size.
To dissipate heat generated by the MicroVCS condenser, ram air is used to move heated air overboard. “There is no significant heat addition to the local environment on the aircraft,” Honeywell told AIN. While the condenser circuit is air-cooled, Honeywell said it could be replaced with a liquid-cooled condenser, “which would be a relatively minor modification.”
MicroVCS has been under development since 2018. The first installation in an Alice airframe is expected later this year, with full qualification scheduled for the second half of 2021. For a UAM or electric aircraft application, MicroVCS not only can cool the cabin but also can provide liquid cooling of batteries and electronic components.
“Aircraft in the emerging UAM or all-electric categories will need to be lightweight and avoid significant downtime for maintenance,” said Tom Hart, v-p and general manager, Honeywell Aerospace Air & Thermal Systems. “It will also be extremely important to maintain battery temperature and ensure passenger comfort. Our new MicroVCS is up to 35 percent lighter and 20 percent more efficient than existing systems, which helps address these major concerns.”